1. Field of the Invention
The present invention relates to a three-dimensional semiconductor integrated circuit apparatus and a manufacturing method therefor.
2. Description of the Related Art
In recent years, attempts have been made to develop three-dimensional semiconductor integrated circuit apparatuses by integrating plural circuit functional blocks three-dimensionally with a view to producing semiconductor integrated circuit apparatuses on a larger scale of integration and in higher density. At first, the possibility of manufacturing three-dimensional semiconductor integrated circuit apparatuses by monolithic technology utilizing xe2x80x9csilicon on insulatorxe2x80x9d (SOI) techniques through laser recrystallization and otherwise to repeat SOI substrate formation and the formation of semiconductor apparatuses over the SOI substrates so prepared. However, stacking many SOI layers involves the problems of the difficulty to secure a satisfactory level of crystallinity and a long manufacturing time.
For this reason, many ways to manufacture three-dimensional semiconductor integrated circuit apparatuses are under study, such as bonding together monocrystalline semiconductor substrates over which semiconductor integrated circuit apparatus are fabricated in advance.
In an article by Yoshihiro Hayashi et al. in the September 1990 issue of the monthly Semiconductor World, pp. 58-64 (in Japanese), as a bonding technique, a CUBIC method is proposed by which semiconductor substrates ground into thin films are bonded together. According to the CUBIC technique, after a first semiconductor substrate having a semiconductor element formed over a silicon substrate is bonded to a supporting substrate, superfluous parts of the silicon substrate are polished off to obtain a thin film. Then, wiring lines needed for the connection of devices including contact members, such as embedded wiring, back side wiring and bump/pools, and the first semiconductor substrate and a second semiconductor substrate having a semiconductor element formed over a silicon substrate are bonded together. Finally, the supporting substrate is removed to finish the intended semiconductor of a multi-layered structure.
Another instance is a three-dimensional semiconductor integrated circuit apparatus formed by a bonding technique, disclosed in the Japanese Published Unexamined Patent Application No. Hei 6-260594. This process begins with similar steps to those of the CUBIC technique, i.e. a first semiconductor substrate having a semiconductor element formed over a silicon substrate is bonded to a supporting substrate, and superfluous parts of the silicon substrate are polished off to obtain a thin film, but it is different in that a trench for embedded wiring is provided in the first semiconductor substrate in advance and that the first semiconductor substrate and a second semiconductor substrate having a semiconductor element formed over a silicon substrate are bonded together, followed by removal of the supporting substrate and formation of embedded wiring.
However, both of these manufacturing processes involve the steps of bonding the first semiconductor substrate to the supporting substrate and to remove the supporting substrate after polishing, resulting in troublesome complexity.
The CUBIC technique involves its own problem that, because the supporting substrate is removed after superfluous parts of the silicon substrate are polished off to obtain a thin film, the integrated circuit formed over the semiconductor substrate is apt to be damaged when the supporting substrate is removed.
Furthermore, the technique disclosed in Japanese Published Unexamined Patent Application No. Hei 6-260594 is subject to a problem that, since the first semiconductor substrate in which a trench for embedded wiring is provided in advance is bonded to the supporting substrate, the adhesive having found its way deep into the trench is difficult to remove and another problem that, because an insulating film is formed by oxidizing the side walls of the trench after the first semiconductor substrate and the second semiconductor substrate are bonded together, the oxidization temperature cannot be raised beyond a level that the adhesive can withstand, making it impossible to form a reliable insulating film.
Therefore, the present invention is intended to provide a three-dimensional semiconductor integrated circuit apparatus which permits ready electrical connection and is highly resistant to deformation. The invention is also intended to provide a manufacturing method for three-dimensional semiconductor integrated circuit apparatuses, which requires no step to mount or dismount a supporting substrate, thereby simplifying the manufacturing process substantially, and permits stacking of multi-layered semiconductor substrates in a simple and easy process and formation of embedded wiring surrounded by a reliable insulating layer.
In order to realize these intentions, according to a first aspect of the invention, there is provided a three-dimensional semiconductor integrated circuit apparatus having a first semiconductor substrate over whose surface layer is formed a first integrated circuit; a second semiconductor substrate over whose surface layer are formed a second integrated circuit and embedded wiring of which one end is electrically connected to the second integrated circuit and the other end is exposed from the back side, and whose integrated circuit side is bonded to the integrated circuit side of the first integrated circuit so that the first integrated circuit and the second integrated circuit be electrically connected; and a third semiconductor substrate over whose surface layer is formed a third integrated circuit and whose integrated circuit side is bonded to the back side of the second integrated circuit so that the third integrated circuit be electrically connected to the other end of the embedded wiring.
This three-dimensional semiconductor integrated circuit apparatus according to the first aspect of the invention, since its first semiconductor substrate and second semiconductor substrate are bonded together with their respective integrated circuit sides positioned opposite to each other, permits ready electrical connection, and its good symmetry effectively prevents the substrates from deformation such as warping. Moreover, as the embedded wiring penetrates the substrate, the substrate can be made reasonably thick.
According to a second aspect of the invention, there is provided a three-dimensional semiconductor integrated circuit apparatus having a first semiconductor substrate over whose surface layer is formed a first integrated circuit; a second semiconductor substrate over whose surface layer are formed a second integrated circuit and embedded wiring of which one end is electrically connected to the second integrated circuit and the other end is exposed from the back side, and whose integrated circuit side is bonded to the integrated circuit side of the first integrated circuit so that the first integrated circuit and the second integrated circuit be electrically connected; and a third semiconductor substrate over whose surface layer are formed a third integrated circuit and embedded wiring of which one end is electrically connected to the third integrated circuit and the other end is exposed from the back side, and whose integrated circuit side is bonded to the back side of the second integrated circuit so that the third integrated circuit be electrically connected to the other end of the embedded wiring of the second semiconductor substrate.
This three-dimensional semiconductor integrated circuit apparatus according to the second aspect of the invention, as embedded wiring is formed in the third semiconductor substrate, makes it possible to manufacture a four-layered three-dimensional semiconductor integrated circuit apparatus by further grinding the back side of the third semiconductor substrate to expose the embedded wiring and by bonding a fourth semiconductor substrate to the back side of the third semiconductor substrate so that the integrated circuit side of the fourth semiconductor substrate over whose surface layer is formed a fourth integrated circuit be electrically connected to the exposed part of the embedded wiring. Further, it is possible to manufacture a three-dimensional semiconductor integrated circuit apparatus of a structure having five or more layers by repeating the same process.
It is possible to electrically connect the other ends of the embedded wiring between the first integrated circuit and the second integrated circuit and between the third integrated circuit and the second semiconductor substrate via contact members such as micro-bumps.
The electrical connection of the other ends of the embedded wiring between the first integrated circuit and the second integrated circuit and between the third integrated circuit and the second semiconductor substrate can be readily accomplished by using contact members such as micro-bumps.
By a first manufacturing method for three-dimensional semiconductor integrated circuit apparatuses according to another aspect of the present invention, a first semiconductor substrate over whose surface layer is formed a first integrated circuit and a second semiconductor substrate over whose surface layer are formed a second integrated circuit and embedded wiring electrically connected to the second integrated circuit are bonded together with their respective integrated circuit sides positioned opposite to each other so that the first integrated circuit and the second integrated circuit be electrically connected; the back side of the second semiconductor substrate is grounded to expose the embedded wiring; and the integrated circuit side of a third semiconductor substrate over whose surface layer is formed a third integrated circuit is connected to the back side of the second semiconductor substrate so that the third integrated circuit be electrically connected to the exposed part of the embedded wiring.
In this first manufacturing method for three-dimensional semiconductor integrated circuit apparatuses according to the invention, as it enables without having to use a supporting substrate or the like a first semiconductor substrate over whose surface layer is formed a first integrated circuit and a second semiconductor substrate over whose surface layer are formed a second integrated circuit and embedded wiring electrically connected to the second integrated circuit to be directly bonded together with their respective integrated circuit sides positioned opposite to each other so that the first integrated circuit and the second integrated circuit be electrically connected, a step of bonding the substrate to a supporting substrate and one of removing them from the supporting substrate is dispensed with, making it possible to substantially simplify the manufacturing process.
Moreover, as many semiconductor substrate layers as desired can be stacked one over another in such a simple and easy process of repetitive alternation of grinding and bonding that the embedded wiring is exposed on the surface layer by grinding the back side of the second semiconductor substrate, and the integrated circuit side surface of the third semiconductor substrate over whose surface layer is formed the third integrated circuit is bonded to the back side of the second semiconductor substrate so that the third integrated circuit be electrically connected to the exposed part of the embedded wiring.
It is further possible to form a reliable insulating film because semiconductor substrates are bonded after the formation of embedded wiring.
It is preferable that the second semiconductor substrate be a silicon substrate having an insulating layer made up of silicon dioxide inside and the back side of the second semiconductor substrate be ground to the insulating layer to expose the embedded wiring.
The use of an insulating layer made up of silicon, dioxide inside as the semiconductor substrate makes it easier to stop grinding just before the insulating layer because silicon dioxide is harder and accordingly more difficult to grind than silicon is.
It is also preferable to bond the first semiconductor substrate to the second semiconductor substrate and the second semiconductor substrate to the third semiconductor substrate by injecting a fluid adhesive into the gaps between the semiconductor substrates, and an epoxy adhesive is particularly preferable as the fluid adhesive.
The use of a fluid adhesive for bonding the semiconductor substrates together make possible uniform injection of an adhesive between the semiconductor substrates. Among fluid adhesives, epoxy fluid adhesives are highly unlikely to generate bubbles, which would adversely affect the electrical performance of the three-dimensional semiconductor integrated circuit apparatus.
In order to achieve the intentions of the invention, by a second manufacturing method for three-dimensional semiconductor integrated circuit apparatuses according to still another aspect of the invention, a first semiconductor substrate over whose surface layer is formed a first integrated circuit and a second semiconductor substrate over whose surface layer is formed a second integrated circuit are bonded together with their respective integrated circuit sides positioned opposite to each other so that the first integrated circuit and the second integrated circuit be electrically connected; the back side of the second semiconductor substrate is grounded to expose the embedded wiring; on the second semiconductor substrate is formed the embedded wiring of which one end is electrically connected to at least either one of the first integrated circuit or the second integrated circuit and the other end is exposed on the back side of the second semiconductor substrate; and the integrated circuit side of a third semiconductor substrate over whose surface layer is formed a third integrated circuit is bonded to the back side of the second semiconductor substrate so that the third integrated circuit be electrically connected to the exposed part of the embedded wiring.
In this second manufacturing method for three-dimensional semiconductor integrated circuit apparatuses according to the invention, as it enables without having to use a supporting substrate or the like a first semiconductor substrate over whose surface layer is formed a first integrated circuit and a second semiconductor substrate over whose surface layer is formed a second integrated circuit to be directly bonded together with their respective integrated circuit sides positioned opposite to each other so that the first integrated circuit and the second integrated circuit be electrically connected, a step of bonding the substrates to a supporting substrate and one of removing them from the supporting substrate is dispensed with, making it possible to substantially simplify the manufacturing process. Moreover, as the embedded wiring penetrates the substrate, the substrate can be made reasonably thick.
Furthermore, according to the invention, a three-dimensional semiconductor integrated circuit apparatus can be manufactured in such a simple and easy process of bonding, grinding and forming embedded wiring that the embedded wiring of which one end is electrically connected to at least either one of the first and second integrated circuits and the other end is exposed on the back side of the second semiconductor substrate is formed and the integrated circuit side of the third semiconductor substrate over whose surface layer is formed the third integrated circuit is bonded to the back side of the second semiconductor substrate so that the third integrated circuit be electrically connected to the exposed part of the embedded wiring.
To add, by further grinding the back side of the third semiconductor substrate to form over the third semiconductor substrate the embedded wiring of which one end is electrically connected at least one of the first, second and third integrated circuits and the other end is exposed on the back side of the third semiconductor substrate, and bonding the integrated circuit side of a fourth semiconductor substrate over whose surface layer is formed a fourth integrated circuit to the back side of the third semiconductor substrate so that the fourth integrated circuit be electrically connected to the exposed part of the embedded wiring, a four-layered three-dimensional semiconductor integrated circuit apparatus can be manufactured, and by repeating this process a three-dimensional semiconductor integrated circuit apparatus of a structure having five or more layers can be manufactured.
It is preferable that the second semiconductor substrate be a silicon substrate having an insulating layer made up of silicon dioxide inside and the back side of the second semiconductor substrate be ground to the insulating layer. The use of an insulating layer made up of silicon dioxide inside as the semiconductor substrate makes it easier to stop grinding just before the insulating layer because silicon dioxide is harder and accordingly more difficult to grind than silicon is.
It is further preferable that the embedded wiring penetrate an insulator region provided in the second semiconductor substrate. The formation of the embedded wiring to penetrate the second semiconductor substrate eliminates the need to form a separate insulating layer because in this way the embedded wiring will have an insulator region around it.